USSG 410 Ga. Single Shot w/26" Barrel/Improved Modified/Synthetic Stock Many have called the MP18 the workhorse of shotguns. This single barrel shotgun is known world wide for quality, durability and craftsmanship. The MP18, with its wood stock and forend is available in 12, 20 and 410 gauge. Features include modified or improved cylinder chokes, 24",26" or 28" barrel and standard or youth size stocks.